1. Technical Field
A polymer electrolyte for an electrochemical half-cell, a half-cell as well as uses of a half-cell and a polymer electrolyte are disclosed.
2. Background Information
Numerous types of half-cells for electrochemical measurements are known, e.g., for potentiometric or amperometric measurements. Such half-cells can be configured in particular as reference electrodes that are used in combination with potentiometric or amperometric sensors. Such reference electrodes provide a reference potential as as constant possible.
In one kind of reference electrode, a liquid reference electrolyte is contained inside a housing, for example an aqueous solution of potassium chloride which can be brought into contact with a liquid measurement medium by way of a liquid connection (also referred to as “liquid junction”). In order to avoid or reduce the occurrence of an undesirable exchange of substance between the measurement medium and the reference electrolyte, the liquid connection can be configured as a more or less porous diaphragm. However, liquid connections of this kind have pores that can become contaminated or even obstructed, which can lead to errors in the electrical potential and possibly to interruptions.
A further type of reference electrode has a single opening or a plurality of openings instead of a diaphragm, whereby the aforementioned contamination can largely be avoided. However, in order to prevent the reference electrolyte from draining out, this configuration uses a reference electrolyte that is not capable of liquid flow instead of using the liquids or gels that form the reference electrolyte. Particularly suitable for this purpose is a polymer electrolyte that is present in the form of a hydrogel containing for example a saturated aqueous solution of potassium chloride, such as with additional potassium chloride in suspended form.
A reference electrode is described in EP 1 124 132 A1, the disclosure of which is hereby incorporated by reference in its entirety. A polymer electrolyte contains a polymer based on monomers selected from N-substituted acrylamides and/or methacrylates. The N-substituted acrylamides are selected for example from N,N-dimethyl-acrylamide, N-(tris(hydroxyl-methyl)-N-methyl-acrylamide, N-hydroxyl-methyl-acrylamide, N-hydroxyl-ethyl-acrylamide, N-glycerin-acrylamide and combinations thereof. The monomers used in this electrode are used to make polymer electrolytes that have an unsatisfactory level of stability against acids and bases, a poor stability against hydrolysis, as well as a low polarity.